The Dual Population Problem: People and Things

As we careen from one crisis to the next, focused on political struggles that seem to rarely produce even short-term solutions, it's easy to avoid big questions that have no easy answers. Here's a good one: What is the sustainable carrying capacity of the planet for Homo sapiens?

Such a process must start with a commitment to a dramatic reduction in per capita consumption in the developed economies and a recognition that the developing world must abandon the goal of achieving the level of consumption that exists in the affluent countries today.

Estimates vary from 500 million to more than one trillion, with the majority of studies putting the number at or below eight billion people. Whatever the answer, we believe that the sustainable carrying capacity of the planet for humans has limits, that it's likely that humans passed a sustainable limit decades ago, and we are able to avoid the consequences of that reality temporarily through exploitation of more dense energy with more advanced technology.

We see no reason to believe that can go on forever. This conclusion does not mean we can do nothing but wring our hands while preaching doom and gloom. We can advocate for collectively setting limits as an important part of rational and responsible planning, which has to be based on an honest assessment of the conditions under which we live today and can expect to live tomorrow.

Such planning requires that we think about more than global warming. Rapid climate destabilization is an existential threat, but it's a derivative of overshoot, of too many people consuming too much stuff in the aggregate. If a miracle solution to climate destabilization appeared tomorrow, we would still face multiple cascading crises because human demands on Earth's ecosystems are in excess of those ecosystems' capacity to regenerate in a time frame relevant to us. Fertility rates are declining in most places, but a slower rate of growth doesn't solve our problems. At some point in the future, there will have to be significantly fewer people and a lot less stuff, either by our choice or through natural forces that we can't control.

The goal of our planning can be stated simply and clearly: fewer and less. Fewer people, less stuff. Justice demands that we achieve a more equitable distribution of the world's resources. Sustainability demands that we confront overshoot.

Many people, including many environmentalists we know, prefer not to talk about the growth of the human population as a problem or about population control as a component of a viable environmental policy. Why? Three reasons seem to push people away from this discussion.

The first is that such concerns about population have been associated with a lack of compassion and/or racism, ethnocentrism, and class prejudice. Historically, some of the people who worried about population growth, going back a couple hundred years to Thomas Malthus, said some pretty cruel things about poor people and argued that any actions based in benevolence toward the poor would be self-defeating because such measures lead to increased population that would make the situation worse. When a legitimate concern about population turns into a rationalization for harsh social Darwinism, it's not surprising that decent people get nervous about the issue.

Today, some of the most vocal supporters of population control also espouse white supremacist and anti-immigrant sentiments. The ugly history of eugenics lurks in the background as well. As a result, any discussion of population growth as a problem can lead to accusations of bigotry or insufficient understanding of the liberating potential of eco-socialism, which tends to shut down necessary conversations. We are grateful that some environmentalists, such as Eileen Crist, are willing to speak bluntly: "The dismal consequences for Earth and for humanity of an oversized global population are indisputable."

The second reason people might avoid the subject is that no one has ever proposed a viable noncoercive strategy for serious population reduction on the scale and in the time frame necessary, because no such strategy exists. Raising the status of women and educating girls, along with family planning, can reduce birthrates, but not at anywhere near the rate that will be necessary to get to a sustainable population. The most well-known experiment in large-scale limitations on births, China's one-child policy, in place from 1980 to 2016, was controversial on moral and political grounds, and researchers still debate how many births it prevented.

The other side of the population equation--the death rate--is even more vexing. The twentieth century saw declines in infant, child, and maternal mortality, along with the invention of medical technology that could extend people's lives. The question about population reduction requires talking not just about how many kids are born but about how long each person lives, and even fewer people want to talk about that side of the population problem. In the 2009 debate about health insurance and the 2012 presidential election, conservatives whipped up hysteria over "death panels," the argument that moving toward universal health care would result in bureaucrats making decisions about who lives and who dies. The ease with which some politicians were able to scare people with such claims indicates how far the United States is from an honest discussion on the subject of the appropriate level of intervention to prevent death, especially as we age. We need such a debate about setting policy, not only on when to withdraw care from the terminally ill, but also on the wisdom of using a range of life-extending medical procedures (e.g., heart bypasses, organ transplants).

While we need to talk about birth control, just as crucially, we need to talk about whether to continue the current level of death control. In the United States, we ration health care by the ability to pay, which means that those with resources can maximize the use of advanced medical care to extend life. If we were to institute a truly equitable system of health-care distribution, the question of death control cannot be avoided. The discomfort with this issue doesn't render the questions irrelevant. As the author of a recent study of human life spans put it, "Many of the key problems we now face as a species are second-order effects of reduced mortality."

Also important to social stability is what is called the dependency ratio, the relationship between people of working age and those who are not working. The youth dependency ratio includes those under the age of fifteen, and the elderly dependency ratio includes those sixty-five and older. A high dependency ratio means working people carry a heavier burden to support those who are not economically active. So if birthrates were to continue to decline, slowing population growth, and people were to continue to live longer, the dependency ratio will rise over time, with dramatic consequences. In the words of an international team of journalists, "The strain of longer lives and low fertility, leading to fewer workers and more retirees, threatens to upend how societies are organized . . . [and] may also require a reconceptualization of family and nation."

The third reason that people may avoid the population issue is that, whether acknowledged or not, everyone recognizes that raw population numbers are meaningless without attention to per capita consumption. That means talking about limits. Imposing limits requires that we distinguish between basic needs (what we truly can't live without, such as food, water, clothing, and shelter), social needs (what's required for humans to flourish, or what we might call enrichment activities such as the arts), and luxuries that we will not be able to support (e.g., not only private jets for the wealthy but also routine air travel for the middle class). It also means talking about redistribution of wealth, not only within societies, but between countries. Those choices require planning within a political process that is committed to the dignity of all people and global solidarity, which requires a willingness to pursue policies with the goal of a rough equality. No such planning has yet happened, and no such political process currently exists. Such a process must start with a commitment to a dramatic reduction in per capita consumption in the developed economies and a recognition that the developing world must abandon the goal of achieving the level of consumption that exists in the affluent countries today. Those goals are not easy to achieve, nor are they fair to everyone, but they are the task ahead.

Those are the impediments, not just to adopting policies, but to even talking about the issue of human numbers and consumption, the dual population problem: the population of people and the population of people's things. Behind all the denial is the techno-optimism that assumes we will always invent our way out of any problem, which may turn out to be the biggest impediment to meaningful change.

If we could overcome these impediments, what should be our goal? What is a sustainable human population? We don't pretend to know, and failed attempts at prediction in the past have made people understandably wary. But it's safe to say that if our goal is long-term sustainability, the number is well below eight billion people. A lot fewer people, consuming a lot less.